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JAVA 使用 Stream 中 Collectors 工具类 基础操作

A邱凌 2022-02-23 阅读 55

求取最大值、最小值、求和、求平均值

 

class A {
    companion object {

        private val list = ArrayList<Test>()

        @RequiresApi(Build.VERSION_CODES.N)
        @JvmStatic
        fun main(args: Array<String>) {
            println("-----------------------------------")
            list.add(Test(120, "语文"))
            list.add(Test(12, "数学"))
            list.add(Test(70, "英语"))
            list.add(Test(92, "化学"))
            list.add(Test(10, "物理"))
            list.add(Test(96, "生物"))
            //求取最大值
            val maxBy = list.stream().collect(Collectors.maxBy(Comparator.comparing(Test::score)))
            //求取最小值
            val minBy = list.stream().collect(Collectors.minBy(Comparator.comparing(Test::score)))
            //平均值 averagingInt\averagingDouble、averagingInt、averagingLong
            val averagingInt = list.stream().collect(Collectors.averagingInt(Test::score))

            println("-maxBy----${maxBy}-minBy-${minBy}---averagingInt-${averagingInt}")
            //summarizingDouble、summarizingInt、summarizingLong  TODO 求得:计数、求平均、求和、最大、最小
            val summarizingInt = list.stream().collect(Collectors.summarizingInt(Test::score))
            println("-summarizingInt--总数--${summarizingInt.count} 总分--${summarizingInt.sum} 平均分--${summarizingInt.average} 最小--${summarizingInt.min} 最大--${summarizingInt.max} ")

        }


    }

    data class Test(var score: Int, val suject: String = "")

}
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